Compressor motor control system



Feb. 24, 1953 H. w. GRAYBROOK EIAL 2,629,537

COMPRESSOR MOTOR CONTROL SYSTEM Filed Aug. 19, 1950 2 SHEETS-SHEET 1 22Fig.l. 54

Reservoir Compressor Main Reservoir Reservoir Compressor Main ReservoirWITNESSES: INVENTORS W Herbert W. Groybrook ugc i Esthel W. Ames.

1953 w. GRAYBROOK ETAL 2,629,537

COMPRESSOR MOTOR CONTROL SYSTEM Filed Aug. 19, 1950 2 SHEETS-SHEET 2Compressor WITNESSES:

INVENTORS Herbert W. Gruybrook and Esrhel W. Ames.

ATTORNEY Patented Feb. 24, 1953 UNITED STATES PATENT OFFICE COMPRESSORMOTOR CONTROL SYSTEM Herbert W. Graybrook, Irwin, and Esthel W.

Ames, Pittsburgh, Pa., assignors to Westinghouse Electric Corporation,East Pittsburgh, Pa., a corporation of Pennsylvania Application August19, 1950, Serial No. 180,382

14 Claims. 1

Our invention relates, generally, to control systems and, moreparticularly, to systems for controlling the operation of electricmotors which drive fluid compressors.

On electric locomotives it is the usual practice to drive the aircompressors with auxiliary motors which are supplied with currentthrough the current collectors on the locomotives. Therefore, the motorsmay be subjected to power interruptions of relatively short duration andit is desirable that the motors be prevented from starting thecompressors against a head pressure after a momentary interruption ofpower.

An object of our invention, generally stated, is to provide a compressormotor control system which shall be simple and eflicient in operationand which may be economically manufactured and installed.

A more specific object of our invention is to provide a compressor motorcontrol system which ensures that the compressor is always unloadedduring starting of the motor.

Another object of our invention is to provide for automaticallymaintaining an adequate supply of compressed air or other fluid in afluid pressure system.

Other objects of our invention will be explained fully hereinafter orwill be apparent to those skilled in the art.

In accordance with our invention, a motor driven compressor is providedwith valves which are opened by fluid pressure whenever the motor isrequired to start the compressor against a head pressure. The valvelifters are actuated by fluid stored in a reservoir which is soconnected in the system that fluid pressure is automatically applied tothe valve lifters when power to the motor is interrupted. The valves areautomatically closed at a predetermined time after power is reapplied tothe motor.

For a better understanding of the nature and objects of our invention,reference may be had to the following detailed description, taken inconjunction with the accompanying drawings, in which:

Figure 1 is a diagrammatic view of a control system embodying theprincipal features of our invention;

Fig. 2 is a diagrammatic view of a modification of the invention;

Fig. 3 is a diagrammatic view of another modification of the invention;and

Fig. 4 is a view, in section, of a portion of a compressor suitable forutilization in the system.

Referring to the drawings, and particularly to Figure l, the systemshown therein comprises a fluid or air compressor I0 which is connectedto a main reservoir I I through a pipe I 2 and a check valve I3, a motorI4 for driving the compressor I0 through a shaft I5, a governor orpressureactuated switch I6, a magnet valve I'l, an electrically operatedswitch I8, a voltage responsive relay I9, a manually operated switch 2I,a battery 22, an electrically operated starting switch 23 and anauxiliary reservoir 24.

The motor I4 may be of the split phase type having a main winding 25 anda starting winding 26 which is connected in series-circuit relation witha resistor or capacitor 21 during starting of the motor. A centrifugallyoperated switch 28 controls the energization of the actuating coil 29 ofthe starting switch 23, thereby controlling the energization of thestarting winding 26 through contact members 3| of the switch 23. Themotor I4 may be supplied with power through power conductors 32 and :33which may be connected to any suitable source of single-phasealternating current power.

As shown in Fig. 4, the compressor I0 may have one or more cylinders 34,each cylinder having a piston 35 disposed therein and a cylinder head 36disposed on top of the cylinder. In accordance with the usual practice aplurality of inlet valves 31 and exhaust valves 38. may be provided inthe cylinder head 36. Valve springs 39 may be provided for biasing thevalves to their closed position.

As explained hereinbefore, a valve lifter M is provided for opening theintake valves 3'! under predetermined conditions. The valve lifter 4Icomprises a plunger 42 having prongs 43 thereon for engaging the valves31, a spring 44 for biasing the plunger 42 outwardly or upwardly, anunloader valve or piston 45 and a spring 46 disposed between the piston45 and the plunger 42. When pressure fluid is admitted through a pipe41, the piston 45 and the plunger 42 are actuated downwardly, therebycausing the prongs 43 to lift or open the inlet valves 31.

As explained hereinbefore, the inlet valves 31 are opened by the valvelifter to prevent the motor I4 from starting the compressor Ill againsta head pressure. As also explained hereinbefore, the motor I4 may besubjected to momentary interruptions of power, particularly when thecurrent for the motor is supplied through a current collecting devicesuch as a pantograph mounted on a locomotive and engaging an overheadtrolley conductor, thereby causing a momentary loss of high speeds thepantograph may bounce from the conductor, thereby causing a momentaryloss of power to the motor. Thus it is necessary to prevent the motorfrom starting the compressor against a head pressure both during normaloperation of the system and also during abnormal conditions such asthose caused by momentary interruptions in the power supply.

In the present system, in the form shown in Fig. 1, the auxiliaryreservoir 24, the governor or pressure-actuated switch IS, the magnetvalve II, the electrically operated switch I8 and the voltage relay I9are utilized to provide the necessary protection for the motor. Thefunctioning of the protective features may be explained by describingthe operation of the system.

During the initial starting period the valves are not lifted and thereis no head pressure since there is no pressure in the main reservoir.The manual switch 2| is closed, in Fig. 1, thereby energizing theactuating coil 48 of the voltage relay I9 through a resistor 49. Asshown the relay I9 is of the time delay type having a dashpot whichdelays the closing of contact members 52 of the relay I9.

When the contact members 52 are closed the coil 53 of the line switch I8and the coil 29 of the starting switch 23 are connected across thebattery 22 through contact members 54 of the pressure actuated switch I6and through the centrifugally operated switch 29, respectively.

The closing of the switches I8 and. 23 connects the motor I4 to thepower source and the motor starts to rotate. When the motor attains apredetermined speed the centrifugal switch 28 is opened, therebydeenergizing the coil 29 of the starting switch 23. The contact members3| of this switch are opened to disconnect the starting winding 26,thereby causing the motor to run with its main winding 25 energized.

When the compressor has filled the main reservoir II and the air systemto a predetermined pressure, the pressure-actuated switch I6 opens itscontact members 54 to interrupt the energizing circuit for the coil 53of the line switch I8. This switch then opens, thereby stopping themotor. At the same time the coil 55 of the magnet valve I'I, which waspreviously energized simultaneously with the energization of the coil 53of the line switch I8, is deenergized, thereby permitting the valvemember 56 to be actuated by a spring 5! to the position shown in thedrawing in which air pressure is diverted from the main reservoir IIthrough a pipe 58, the magnet valve I! and the pipe 41 to the auxiliaryreservoir 24 and the valve lifter 4| When the air pressure in the mainreservoir I I drops to a predetermined value the pressureactuated switchIt closes the battery circuit, thereby causing the line switch I3 to bereclosed to reapply power to the motor I4. At this time the coil 55 ofthe magnet valve I1 is also energized, thereby actuating the valvemember 55 to stop the flow of air from the main reservoir I I to theauxiliary reservoir and the valve lifter M, and to permit the airpressure in the auxiliary reservoir 24 and the valve lifter 4! to beexhausted at a predetermined rate throu h a restricted opening 59 in themagnet valve I'I. Thus, the motor is permitted to attain full speedbefore the valves in the compressor are permitted to seat and thecompressor begins pumping against the main reservoir head pressure.

If there should be a momentary interruption of the alternating-currentsupply the time delay relay I9 will drop out immediately, therebyinterrupting the energizing circuits for the line switch I8, thestarting switch 23 and the magnet valve I'I. Because of the time delayconstruction of relay I9 it can not reconnect the battery circuits tocause starting of the motor even though power is reapplied to theconductors 32 and 33 until sufiicient time has elapsed to lift thevalves in the compressor.

In this manner the motor I4 is permitted to startthe compressor unloadedunder all conditions, thereby preventing damage to the motor. Anadequate supply of compressed air is assured since the motorautomatically starts the compressor (if the pressure-switch contacts 54are closed), after power interruptions of short duration.

In the modification shown in Fig. 2, in which like parts are designatedby the same reference characters as in Fig. 1, the voltage relay I9 isomitted and the battery circuit is closed and opened by a thirdswitch-blade or contact member 6| on the manually perated switch 2 I.Also, an additional contact member 62 is provided on the centrifugalswitch 28. Otherwise the system shown in Figure 2 is similar to the oneshown in Figure 1.

The motor I4 is initially started, in Fig. 2, by closing the manualswitch 2I. When the motor attains a predetermined speed the centrifugalswitch 28 opens the energizing circuit for the starting switch 23 andcloses the energizing ircuit for the magnet valve II. If for any reasonthe motor voltage fails or allows the motor speed to drop to a pointWhere the centrifugal switch 28 drops back to its starting position, themagnet valve circuit is opened, thereby permitting the air pressure fromthe main reservoir to fill the auxiliary reservoir 24 and to lift thevalves in the compressor.

When the motor starts again, and attains a certain intermediate speed,in Fig. 2, the centrifugal switch 28 closes the magnet valve circuit,thereby permitting the air in the auxiliary reservoir 24 and the valvelifter 4| to exhaust through the magnet valve and the valves to seat.The compressor then starts building up pressure in the main reservoir inthe manner previously described.

In the modification of the invention shown in Figure 3 a startingpush-button switch 63, an auxiliary contact member 64 on the line switchI8, and an auxiliary pressure-actuated switch 65 are provided, inaddition to the apparatus shown in Fig. 1. Also, the time delay device5I is omitted from the voltage relay I9. Otherwise the system shown inFig. 3 is similar to the one shown in Fig. 1.

To ready the motor I4 for starting, the manual switch 2I is closed,thereby energizing the voltage relay I9. The starting push button 63 isdepressed to close its contact members 66, thereby energizing the lineswitch I8 and the starting switch 23, from a battery-energized circuitincluding the contacts 52 and 54. The auxiliary contact 64 on the lineswitch I8 establishes a holding circuit for the line switch I8 and thestarting switch 23, thereby permitting the pushbutton switch 63 to bereleased after these switches have closed. The motor l4 starts and at apredetermined speed the centrifugal switch 28 opens the starting switch23.

After the compressor has filled the air reservoir II to a predeterminedpressure, the pressureactuated switch l6 opens the circuits for theline. switch 18 and the magnet valve i! in the manner previouslydescribed. It should be noted that the magnet valve H in Fig. 3 wasenergized through contact members 6'! on the push-button switch 63 whenthis switch was released after starting the motor. When the magnet valveI7 is deenerized the auxiliary reservoir 24 is filled and air pressureis applied to the valve lifter 4| to lift the valves in the mannerpreviously described.

When the air pressure in the main reservoir has dropped to apredetermined value the pressure-actuated switch l6 closes the circuitto the line contaotor l8 and the starting switch 23 provided there is aminimum predetermined pressure in the auxiliary reservoir 24 as measuredby the auxiliary pressure switch 65 of Fig. 3. As shown, contact members53 on the switch 65 establish a circuit through conductors 69 and I!which parallels the circuit through the contact members 66 of thepush-button switch 63, and also parallels the circuit through thecontact members 64 of the switch it. The pressure in the auxiliaryreservoir 24 prevents the valves from seating, so that the compressor isunloaded and the motor can not start under load. At this time the magnetvalve I7 is energized, thereby permitting the air from the reservoir 24to be exhausted at a predetermined rate as previously explained. Whenthe pressure has decreased to a predetermined value the valves arepermitted to close and the compressor starts pumping.

If there should be a momentary interruption in the alternating-currentsupply, in Fig. 3, the voltage relay it drops out, thereby opening theline switch it immediately. The magnet valve ll is also deenergized atthis time. When the voltage relay l 9 is again energized by therestoration of power the compressor and the motor are prevented fromstarting unless the valves have been lifted by a predetermined pressurein the auxiliary reservoir 24 as measured by the auxiliary pressureswitch 55.

As previously explained it is necessary for the contact members 68 ofthis auxiliary pressure switch 65 in Fig. 3 to be closed in order forthe motor to be restarted automatically. When the pressure in theauxiliary reservoir 2-! is sufficient to close the contact members 68 ofthe switch 65 the motor is automatically started upon the restoration ofpower (assuming that the main pressure-switch contacts 54 are closed),and the valves are lifted in the manner hereinbefore de scribed. 2c isnot sufficient to actuate the auxiliary pressure switch 65, the motorwill not automatically start. In this manner damage to the motor isprevented.

From the foregoing description it is apparent that we have provided acontrol system which automatically controls the starting and stopping ofa compressor motor and prevents the motor from being started against ahead pressure, thereby preventing injury to the motor. The systemdescribed herein provides for automatically restarting the motor aftermomentary interruptions of power, thereby insuring an adequate supply ofcompressed air or other pressure fluid at all times during the operationof the locomotive or other vehicle on which the system is installed.

Since numerous changes may be made in the above described constructionand different embodiments of the invention may be made without departingfrom the spirit and scope thereof, it

If the pressure in the auxiliary reservoir 6 is intended that all mattercontained in the foregoing description or shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

We claim as our invention:

1. In a control system, in combination, a fluid compressor having afluid-actuated valve lifter therein, a motor for driving the compressor,power conductors, electrically controlled switching means for connectingthe motor to the power conductors, a main reservoir connected to thecompressor, an auxiliary reservoir connected to the valve lifter,electrically operated valve means for controlling the admission ofpressure fluid from the main reservoir to the auxiliary reservoir, a,fluid-actuated switch responsive to the pressure in the main. reservoirfor controlling the operation of said switching means and said valvemeans, and relay means responsive to the volt age across said powerconductors for also controlling the operation of said switching meansand said valve means.

2. In a control system, in combination, a fluid compressor having afluid-actuated valve lifter therein, a motor for driving the compressor,power conductors, electrically controlled switching means for connectingthe motor to the power conductors, a main reservoir connected to thecompressor, an auxiliary reservoir connected to the valve lifter,electrically controlled valve means for controlling the admission ofpressure fluid from the main reservoir to the auxiliary reservoir andthe valve lifter and for controlling the exhausting of the pressurefluid from the valve lifter and the auxiliary reservoir, afluid-actuated switch responsive to the pressure in the main reservoirfor controlling the operation of said switching means and said valvemeans, and time delay relay means responsive to the voltage across saidpower conductors for also controlling the operation of said switchingmeans and said valve means.

3. In a control system, in combination, a fluid compressor having afluid-actuated valve lifter therein, a motor for driving the compressor,power conductors, electricall controlled switching means for connectingthe motor to the power conductors, a main reservoir connected to thecompressor, an auxiliary reservoir connected to the valve lifter,electrically operated valve means for controlling the admission ofpressure fluid from the main reservoir to the auxiliary reservoir, afluid-actuated switch responsive to the pressure in the main reservoirfor controlling the operation of said switching means and said valvemeans, and relay means responsive to the voltage across said powerconductors for also controlling the operation of said switching meansand said valve means, said relay means having a device thereon fordelaying the closing of the relay contact members.

l. In a control system, in combination, a fluid compressor having afluid-actuated valve lifter therein, a motor for driving the compressor,power conductors, electrically controlled switching means for connectingthe motor to the power conductors, a main reservoir connected to thecompressor, an auxiliary reservoir connected to the valve lifter,electrically operated valve means for controlling the admission ofpressure fluid from the main reservoir to the auxiliary reservoir, afluid-actuated switch responsive to the pressure in the main reservoirfor controlling the opera tion of said switching means and said valvemeans, relay means responsive to the voltage I across said powerconductors for also controlling the operation of said switching meansand said valve means, and an additional fiuid-actuated switch responsiveto the pressure in the auxiliary reservoir cooperating with said relaymeans.

5. In a control system, in combination, a fluid compressor having afluid-actuated valve lifter therein, a motor for driving the compressor,power conductors, electrically controlled switching means for connectingthe motor to the power conductors, a main reservoir connected to thecompressor, an auxiliary reservoir connected to the valve lifter,electrically operated valve means for controlling the admission ofpressure fluid from the main reservoir to the auxiliary reservoir, afluid-actuated switch responsive to the pressure in the main reservoirfor controlling the operation of said switching means and said valvemeans, relay means responsive to the voltage across said powerconductors for also controlling the operation of said switching meansand said valve means, an additional fluid actuated switch responsive tothe pressure in the auxiliary reservoir cooperating with said relaymeans, and auxiliary contact members on said switching means connectedin parallel-circuit relation to the contact members on said additionalfluidactuated switch.

6. In a control system, in combination, a fluid compressor having afluid-actuated valve lifter therein, a motor for driving the compressor,power conductors, electrically controlled switching means for connectingthe motor to the power conductors, a main reservoir connected to thecompressor, an auxiliary reservoir connected to the valve lifter,electrically operated valve means for controlling the admission ofpressure fluid from the main reservoir to the auxiliary reservoir, afluid-actuated switch responsive to the pressure in the main reservoirfor controlling the operation of said switching means and said valvemeans, relay means responsive to the voltage across said powerconductors for also controlling the operation of said switching meansand said valve means, an additional fluid-actuated switch responsive tothe pressure in the auxiliary reservoir cooperating with said relaymeans, auxiliary contact members on said switching means connected inparallel-circuit relation to the contact members on said additionalfluid-actuated switch, and a manually-operable switch having contactmembers connected in parallel-circuit relation to both said auxiliarycontact members and the contact members on said additionalfluid-actuated switch.

7. In a control system, in combination, a fluid compressor having afluid-actuated valve lifter therein, a motor for driving the compressor,power conductors, switching means for connecting the motor to the powerconductors, a main reservoir connected to the compressor, an auxiliaryreservoir connected to the valve lifter, a magnet valve for controllingthe admission of pressure fluid from the main reservoir to the auxiliaryreservoir, a fluid-actuated switch responsive to the pressure in themain reservoir for controlling the operation of said switching means andsaid magnet valve, and switching means responsive to the motor speed foralso controlling the operation of said magnet valve.

8. In a control system, in combination, a fluid compressor having afluid-actuated valve lifter therein, a motor for driving the compressor,power conductors, switching means for connecting the motor to the powerconductors, a mainreservoir connected to the compressor, an auxiliaryreservoir connected to the valve lifter, a magnet valve for controllingthe admission of pressure rluid from the main reservoir to the auxiliaryreservoir, a fluid-actuated switch responsive to the pressure in themain reservoir for controlling the operation of said switching means andsaid magnet valve, and a centrifugal switch actuated by the motor foralso controlling the operation of said magnet valve.

9. In a control system, in combination, a fluid compressor having afluid-actuated valve lifter therein, a motor for driving the compressor,power conductors, switching means for connecting the motor to the powerconductors, a main reservoir connected to the compressor, an auxiliaryreservoir connected to the valve lifter, a magnet valve for controllingthe admission of pressure fluid from the main reservoir to the auxiliaryreservoir, a -fluid--actu2d;ed switch responsive to the pressure in themain reservoir for controlling the operation of said switching means andsaid magnet valve, a centrifugal switch actuated by the motor for alsocontrolling the operation of said magnet valve, and a manually operableswitch cooperating with said centrifugal switch.

10. A motor-operated fluid-pressure assembly, comprising electricalpower-supply conductors subject to momentary power-interruptions, anelectric motor, main switchin -neans for energizing said motor from saidsupply-conductors, a fluid compressor, a mechanical driving-connectionbetween said motor and said compressor, a fluid-pressure reservoirconnected to said compressor, a fluid-pressure-operated unloader forunloading said compressor in response to the application of apredetermined fluid-pressure to said unloader, an electrcmagneticallyoperated fluid-valve-means, including a valve-magnet, for normallyconnecting said unloader to said reservoir to unload said compressorwhen the valvemagnet is deenergised, and for responding to anenergization of the valve-magnet by disconnecting said unloader fromsaid reservoir and slowly venting said unloader in a time which allowsthe motor sufficient time for starting and attaining an operativemotor-speed before the compressor becomes loaded, and under-pressuremeans, responsive to a predetermined minimum desired fluid-pressure insaid reservoir, for both causing said main switchingsneans to assume amotorenergizing condition and also energizing said valve-magnet, incombination with an auxiliary switching-means, responsive to adeenergized motor-condition, for opening the energizingcircuit of saidvalvecnagnet.

11. The invention as defined in claim 10, characterized by saidauxiliary switching-means being also operative to open said mainswitching-means, in combination with means for subsequently reclosingsaid main switching-means and reenergizing said valve-magnet after theunloader has had time to unload the compressor.

12. The invention as defined in claim 10, characterized by saidauxiliary switching-means being also operative to open said mainswitchingmeans, and further characterized by said auxiliaryswitching-means being a voltage-responsive switching-means which dropsout quickly in response to a predetermined drop in voltage in saidpower-supply conductors, and which picks up slowly enough to give theunloader time to unload the compressor in response to a restoration ofvoltage in said power-supply conductors.

13. The invention as defined in claim 10, char acterized by said motorhaving a speed-responsive means associated therewith for responding toan intermediate motor-speed during the starting of the motor, andfurther characterized by said auxiliary switching-means being amake-contact on said speed-responsive means, said make-contact closingin response to a predetermined speed during motor-acceleration andopening in response to a predetermined speed during motordeceleration.

14. The invention as defined in claim 10, characterized by saidauxiliary switching-means being also operative to open said mainswitchingmeans, in combination with means responsive to 10 theattainment of an efiective operative-pressure on the unloader forreclosing said main switching-means and reenergizing said valve-magnet.

HERBERT W. GRAYBRIO'OK- ESTHEL W. AMES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,134,693 Bartholomew Nov. 1,1938 2,256,565 Mantle Sept. 23, 1941

